A wireless system operates under a large dynamic range of conditions. For example, the wireless system may be subject to a path loss as low as 30-40 decibels (dB) when a client device (e.g., handset, wireless device or user equipment) and a station (e.g., base station) are in close proximity and/or experience a path loss, which can exceed 150 dB for large cells, when the client device is at an extreme edge of coverage.
To operate with this large dynamic range, a receive chain and transmit chain of the client device are designed to support a large range of receive and transmit gains. Given that the base station or access point serves many client devices, the base station transmits downlink signals at a constant power (e.g., close to the base station's maximum power) to ensure that packets transmitted by the base station reach the furthest client devices. Accordingly, the burden falls upon the handset or client device to adjust its receiver gain. When the client device is close to the base station and the receive signal strength is large, the client device reduces the receiver gain and increases the linearity of the receiver to prevent an overload condition. When the client device moves away from the base station and a signal strength of a received signal from the base station drops, the wireless device increases its receiver gain to maintain an adequate signal to noise ratio. Ideally, the ability to dynamically adjust the receiver gain should not compromise a desired noise figure of the receiver because a small noise figure is a key performance parameter when operating near the cell edge.
Regarding uplink, the base station receives packets from multiple client devices simultaneously. In some systems (e.g., orthogonal frequency division multiple access (OFDMA) based systems such as Long Term Evolution (LTE) or 802.11ax), uplink signals from multiple client devices may be transmitted towards the base station simultaneously, in a same time slot, by using different resource blocks or subcarriers. To ensure that a receiver of the base station is not subject to an excessively large dynamic range, transmit power of the multiple client devices are controlled by a feedback loop. The feedback loop provides control to the respective signals of the client devices so that the respective signals arrive at the base station receiver within a desired range of a received signal strength indication (RSSI).
When a received signal strength indication of a client device at the base station receiver is above or below a target received signal strength indication, the client device receives a request to either decrease or increase its transmit power. The request may be received based on a transmit power control loop. It is therefore desirable for a transmit chain of a client device or a customer premise equipment (CPE) to adjust the transmit power over a large range.